The multifunctional role of cullet as an endless cradle to cradle sustainable material has resulted in its increased use within the glass industry. This is even more pronounced in light of recent spiraling energy prices. However, availability of high quality post consumer cullet is a challenge due to contamination during the recycling process. So far to the author's knowledge, there are no systematic methods to determine the type of contamination and also to express the severity of said contamination in a truck load or a pile of cullet. This work in one embodiment establishes a practical quality index to specify cullet quality by type and severity of contaminants. This coding method can be used by all parties involved in the life cycle of cullet (i.e. cullet suppliers and glass manufacturing industries).
Cullet can be used in the glass manufacturing process in any percentage up to ˜90% depending on availability, quality and price. The advantages of addition of cullet to raw batch can be summarized as:    1. Cullet accelerates the melting process by wetting the batch materials and hence aiding decompositions and/or reactions to take place faster.    2. Based on empirical data, every 10% of cullet can result a saving of ˜3-4% in energy consumption.    3. Use of cullet improves sustainability by reducing the quarrying of virgin raw materials; every 100 tons of cullet results in a reduction of 120 tons of virgin materials, assuming normal fusion loss factors.    4. As a result of the aforementioned benefits of reducing energy and reduction of raw materials, cullet results in reduced emitted gases like CO2, SOx and NOx.
Various embodiments of the present invention establish a practical quality index to specify quality of cullet as far as type and severity of contaminants. Some embodiments of the inventive method of coding described herein can be used by all parties in the life cycle of cullet i.e. cullet suppliers and glass manufacturing industries.